Backplane Header for Dense Signal Routing
The 5536501-2: It sits on a 0.079" (2.00mm) pitch across 4 rows, which gives you a dense signal interface for backplane card cages where board real estate is tight.
The board guide helps with alignment when you're sliding a daughtercard into a backplane — without it, the 48 pins can bind before they seat. The mating half is a Z-PACK Futurebus receptacle (the female counterpart in the same series), which accepts this header's male pins. The 4-row, 2.00mm pitch layout means the PCB footprint needs to match that grid exactly; verify the hole pattern against the product drawing before committing the board layout.